Phthalocyanine photoconductive elements containing multiple binder materials

ABSTRACT

Improved electrophotographic elements comprising specific phthalocyanine pigments dispersed in specific binder materials in specific proportions are disclosed. Electrophotographic processes employing said elements are also disclosed.

O Umted States Patent [151 3,640,710 Mammino et al. Feb. 8, 1972 [54] PHTHALOCYANINE PHOTOCONDUCTIVE ELEMENTS References i d CONTAINING MULTIPLE BINDER FOREIGN PATENTS 0R APPLICATIONS MATERIALS 1,447,277 6/1966 France ..96/ l .5 [72] Inventors: Joseph Mammino; Robert M. Ferguson,

both of Penfield, N.Y. Primary Examiner-George F. Lesmes Assistant Examiner-John C. Cooper [73] AssIgnee. Zerox Corporauon, Rochester, NY. Attorney james L Ralabate. Albert A. Mahasse] and [22] Filed: Dec. 31, 1969 Anthony W. Karomdelas [2l] Appl. No.: 889,718 [57] ABSTRACT Improved electrophotographic elements comprising specific [52] US. Cl ..96/l.5, 96/1, 96/ 1.4, phthalocyanine pigments dispersed i specific binder i 252/501 260/28 260/824 als in specific proportions are disclosed. Eleetrophotographic Int. Cl. ..G03g 13/22, 603g 5/06 processes employing i elements are also disc]sed Field oi Search ..96/l.5, 1; 252/501; 260/28, 260/824 19 Claims, No Drawings PHTHALOCYANINE PHOTOCONDUCTIVE ELEMENTS CONTAINING MULTIPLE BINDER MATERIALS BACKGROUND OF THE INVENTION This invention relates to electrophotography and more particularly to a binder plate usable in xerography.

In the art of xerography as originally disclosed by Carlson in US. Pat. No. 2,297,691, an electrostatic latent image is formed on a photoconductive insulating layer and is developed thereon by finely divided electroscopic developing materials. The developed image may then be fixed in place or transferred to a copy sheet where it is permanently fixed. Generally the photoconductive insulating layer is first charged to sensitize it and is then exposed to a light image or other pattern of activated electromagnetic radiation to dissipate the charge in radiation struck areas. Thus the charge pattern formed conforms to the electromagnetic radiation pattern which impinges upon the plate. This charge pattern may then as above discussed be developed or made visible by a chargewise deposition on the plate of an electroscopic or electrostatically attractable, finely divided colored material which is referred to in the art as toner.

As disclosed in the above-noted Carlson patent, suitable inorganic and organic materials may be used to form the photoconductive insulating layer on which the latent electrostatic image is formed. Other photoconductive materials have been disclosed in the prior art as being useful in similar electrophotographic processes such as in US. Pat. Nos. 2,357,809; 2,891,001; and 3,079,342. Some of these materials are vitreous selenium, polymers such as polyvinylcarbazole, and resin suspensions of inorganic photoconductive pigments such as, for example, zinc oxide and cadmium sulfide. While most of these materials have evidenced some commercial utility, there are certain inherent disadvantages to the commercial use of each of the suggested compositions.

The discovery of the photoconductive insulating properties of highly purified vitreous selenium has resulted in this material becoming the standard in commercial xerography. Vitreous selenium, however, is sensitive only to wavelengths shorter than about 5,800 A. U. In addition, xerographic plates made with selenium are expensive to manufacture since this material must be applied to the supporting substrate by vacuum evaporation under carefully controlled conditions. Also, vitreous selenium layers are only metastable and may be recrystallized into inoperative crystalline forms at temperatures only slightly in excess of those prevailing in conventional xerographic copying machines.

Other known xerographic plates made with certain aromatic organic photoconductors have relatively low sensitivity to light and have most of this sensitivity in the ultraviolet range, which is not fully satisfactory for use in conventional electrophotographic copying devices. Even the most sensitive organic photoconductive polymers leave much to be desired for commercial purposes. The choice of materials available for use in aromatic polymeric plates is of course limited because of the necessity of the selection of an already photoconductive material. In addition, all of the above noted xerographic plates lack abrasion resistance and stability of operation particularly at elevated temperatures.

Binder plates containing zinc-oxide pigments, while comparatively inexpensive, are lower in sensitivity as compared with vitreous selenium plates and are not reusable. Also, as above noted, their visible sensitivity is quite limited. Furthermore, it is necessary to use such high percentages of photoconductive pigment in order to attain adequate sensitivity that it is difficult in zinc oxide plates to obtain smooth surfaces which lend themselves to efficient toner transfer and subsequent cleaning prior to reuse. An additional drawback in the use of zinc oxide binder type plates is that they can be sensitized only by negative and not by positive corona. This property makes them commercially undesirable since negative corona discharge generates much more ozone than positive corona discharge and is generally harder to control.

2 SUMMARY or THE INVENTION It is, therefore, an object of this invention to provide an electrophotographic material devoid of the above-noted disadvantages.

Another object of this invention is to provide electrophotographically reusable or nonreusable plates having sensitivities which extend over substantially the entire visible spectrum and which produce superior prints.

Still another object of this invention is to provide a glossy electrophotographic coating.

Yet another object of this invention is to provide an electrophotographic element with improved flexiblity and adhesion properties.

Still another object of this invention is to provide a reusable or nonreusable electrophotographic plate at a substantially reduced cost.

A further object of this invention is to provide an electrophotographic plate which will produce images of higher contrast.

Another further object of this invention is to provide an electrophotographic plate which will produce final copies having reduced ink background.

Yet another further object of this invention is to provide a novel electrophotographic process utilizing either a reusable or nonreusable plate which produces superior prints devoid of substantially all ink background.

The foregoing objects and others are accomplished in accordance with this invention, generally speaking, by providing a novel photoconductive layer comprising a phthalocyanine pigment selected from the group consisting of the alpha-form, beta-form, X-form, and mixtures thereof, a resin blend of alkyd and acrylic resins, a silicone resin, and a chlorinated hydrocarbon. The photoconductive layer so formed is placed on a suitable substrate or cast as a self supporting member to produce an imaging member. The imaging member is charged, exposed and developed using conventional techniques. This novel photoconductive layer has particular utility in either a reusable or nonreusable electrophotographic system. Further, said layer is glossy and produces images of superior quality than heretofore known images. In addition, the final copies produced are devoid of substantially all ink background. Finally, the images produced are of higher contrast than heretofore known images produced with phthalocyanine pigment-binder plates or other known electrophotographic plates. As above described, the phthalocyanine-binder photoconductive layer may be cast as a self-supporting film, or in lieu thereof may be deposited on any suitable supporting substrate. The plate formed may be both with or without an overcoating on the photoconductive layer. As a third alternative to the above noted self-supporting layer and substrate supported layer, the phthalocyanine-resin photoconductive layer may be used in the formation of multilayer sandwich configuration xerographic plates. I

When it is desired to coat the phthalocyanine-binder film on a substrate, any suitable supporting materials may be used. Typical supporting materials include paper, aluminum, steel, brass, metallized or tin oxide coated glass, semiconductive plastics, and resins, and any other convenient material. Any suitable dielectric material may be used to overcoat the photoconductive layer. Typical overcoatings include bichromated shellac, nitrocellulose and cellulose acetate.

The phthalocyanine pigments may beincorporated in the dissolved or melted binder by any suitable means such as strong shear agitation, preferably with simultaneous grinding. These methods include ball milling, roller milling, sand milling, ultrasonic agitation, high speed blending and any desirable combination of these methods. In addition to adding the phthalocyanine pigment to the dissolved or melted binder material it may also be added and blended into a dry or slur ried form of the powdered binder material before it is heated or dissolved to make it film forming.

Any suitable phthalocyanine may be used in the plates and processes of the instant invention. Typical such phthalocyanines in order of their increasing desirability for use in the system of the present invention include alpha, beta and X- form phthalocyanine. Of these the metal-free phthalocyanine including alpha, beta, X-form and mixtures thereof are preferred. The alkyd-acrylate resin blend present in the photoconductive layer serves as a superior film-forming material and imparts improved flexibility and adhesion to the coating, as compared to other film forming materials.

Any suitable alkyd-acrylate resin blend may be used in the system of the present invention. Typical such resins are more fully described in US. Pat. No. 3,437,481. The silicone resin is present as a pigment dispersant and leveling component and imparts water-vapor moisture resistance to the layer. Any suitable silicone resin may be employed in the system of the present invention. Typical silicone resins include phenyltrichlorosilane, diphenyldimethoxysilane, methylphenyldiethoxysilane and dimethylphenyldichlorosilane. Other resins include those prepared from diphenyltrichlorosilane, dinaphthylsilanediol, anthracenetrichlorosilane, biphenylenetrichlorosilane, fluorenetrichlorosilane and 9,9-dicarbazalolyldichlorosilane.

A chlorinated hydrocarbon is used as a binder-resin constituent because of its excellent compatibility with the other binder resins present. Further, the use of chlorinated hydrocarbons allows one to reduce the amount of phthalocyanine pigment employed from about 1 part by weight of pigment to 6 parts, by weight, of binder to about 1 part pigment at about 12 parts binder without significantly altering the photosensitivity and charge acceptance properties of the layer. Any suitable chlorinated hydrocarbon which is film forming may be used in the system of the present invention. Preferred such hydrocarbons include chlorinated polyolefins, and chlorinated paraffins such as Chlorowax-7OLP, a chlorinated paraffin obtained from Diamond Shamrock Chemical Company. In addition, other suitable organic materials may be employed as a binder resin. Typical such organic materials include petroleum hydrocarbons, styrene, styrene-butadiene copolymers, polyethylene, and polypropylene.

While any suitable ratio of ingredients may be used in the coating formulation of the present invention, preferred results (i.e., superior prints) are obtained when the following formulation is employed:

about 1-2 parts, by weight, of alpha, beta and/or X-form metal-free phthalocyanine;

about 2-4 parts, by weight, of silicone resin;

about 6-12 parts, by weight, of a chlorinated unpolymerized resinous paraffin; and

about 6-13 parts, by weight, of an alkyd acrylic resin.

Optimum results are obtained when the following formulation is employed:

about 1 part, by weight, of alpha, X-fonn, and/or beta form metal-free phthalocyanine;

about 2.5 parts, by weight, of silicone resin;

about 7 parts, by weight, of a chlorinated unpolymerized resinuous paraffin; and

about 7 parts, by weight of an acrylic resin.

The pigment-binder-coat, may be applied to substrates by any of the well known painting or coating methods, including spray, flow coating, knife-coating, electrocoating, Mayer bar drawdown, dip coating, reverse roll coating, etc. Spraying in an electric field may be preferred for smoothest finish and dip coating for convenience in the laboratory. The setting, drying, and/or curing steps for these plates are generally similar to those recommended for films of the particular binders used for other painting applications.

The thickness of the phthalocyanine films may be varied from about 1 to hundreds of microns, depending on the required individual needs. Self-supporting films, for example, cannot usually be manufactured in thicknesses thinner than about 25' microns, and are easiest to handle and use in the 75 to 175 micron range. Coatings, on the other hand, are preferable in the 3 to 80 micron range for most uses. For certain compositions and purposes it is desirable to provide an overcoating; this should usually not exceed the thickness of the photoconductive coating, and preferably not above onefourth of the latter. Any suitable overcoating material may be used such as bichromated shellac or cellulose acetate.

While any suitable substrate may be used in the present invention, it is preferred that a conductive treated paper be employed when the coating is to be used in a nonreusable electrophotographic system. Typical such treated papers include Reigel Paper Corporation conductive treated paper EC40AA and Weyerhaeuser Company carbon black subbed paper (E. P. Graphic, Grade No. 9080-8).

DESCRIPTION OF THE PREFERRED EMBODIMENTS To further define the specifics of the present invention the following examples are intended to illustrate and not limit the particulars of the present invention. Parts and percentages are by weight unless otherwise indicated.

EXAMPLE I The following materials are combined in a ball milling jar, one-third full of lye-inch diameter flint pebbles and roller milled for about 20 hours at about rpm.

about 144 g. of alpha-form metal-free phthalocyanine (obtained from Holland-Suco Color Co.

about 960 g. of Arotap EP891 1-7-7, an alkyd-acrylate resin at 60 percent solid in a xylene butanol solvent blend (obtained from ADM Chemicals);

about 328 g. of Silicone Resin SR-82, a silicone resin at 60 percent solids in xylene (obtained from General Electric Co.);

about 960 g. of Chlorowax 70-LP and about 2700 g. of toluene.

The alpha-phthalocyanine consistently crystallizes to the more sensitive beta-form under these conditions. The pigment dispersion is filtered through a 200 mesh nylon screen and the coating viscosity is adjusted to about -175 centipoise at 24 C. by the addition of toluene, as measured using a Brookfield RVK viscometer with a No. 2 spindle at a speed setting of 50.

A No. 16 wire rod is used to meter the coating formulation upon a Riegel Paper Corporation conductive treated paper EC40AA substrate. The substrate is coated to a dry thickness of about 0.25 mils (6 microns).

The phthalocyanine pigment-binder coated paper is charged, exposed imagewise and developed by means of liquid development employing methods more fully described in US. Pat. NO. 3,084,043. The developer used is a liquid developer such as is described in US. Pat. No. (or copending application Ser. No. 839,801 The toner image is then transferred to ordinary bond paper. An image of excellent quality is obtained.

EXAMPLE ll Example I is repeated using the following formulations:

about 150 g. of beta-form metal-free phthalocyanine;

about 1000 g. of Arotap 3205 XB-60 percent solids in a solvent blend of xylene-butanol (obtained from ADM Chemicals);

about 600 g. of SR-82, a silicone resin at 60 percent solids in xylene obtained from General Electric Co.

about 100 g. of 310-6, a chlorinated polyolefin sold by Eastman Chemical Products Inc., and

about 300 g. of toluene.

An image of superior quality is obtained.

EXAMPLE lll Example I is repeated using a carbon black subbed paper substrate, E. P. Graphic, Grade No. 9080-8, sold by Weyerhaeuser Company. Similar results to those produced in Example l are obtained.

EXAMPLE iv A formulation such as the one mentioned in Example II is prepared and coated on a 5 ml. aluminum foil with a No. 40 drawdown rod. The coating is dried for about 5 minutes at about 125 C. The resulting electrophotographic plate is charged, exposed imagewise and cascade developed in a commercial xerographic apparatus described as Xerox Number 1 Camera and using a Xerox Plate Processor apparatus. The developer used in a commercially available xerographic developer such as is described in US. Pat. No. 2,788,288 and 3,079,312. The toner image is electrostatically transferred to paper and the residual toner is released and wiped off in normal fashion. The plates are then twice cyclically recharged, reexposed, and developed. Prints of superior quality are obtained from the reusable plate.

EXAMPLE V Example I is repeated using the following formulation:

about 100 g. of X-form metal free phthalocyanine;

about 900 g. of Arotap EP891l-77, an alkyd-acrylate resin, obtained from ADM Chemicals, at 60 percent solids in a solvent blend composed of xylene and butanol; about 600 g. of silicone resin SR-82, obtained from General Electric Company, at 60 percent solids in xylene; about 200 g. of Unichlor 70AX, a chlorinated hydrocarbon,

. obtained from Neville Chemical Company;

about 100 g. of Syloid No. 244, a silica pigment obtained from W. R. Grace Company.

The phthalocyanine pigment binder coated paper is charged, exposed imagewise and developed by means of liquid development employing methods more fully described in US. Pat. No. 3,084,043. The developer used in a liquid developer such as described in copending application Ser. No. 839,801. An image of excellent quality is obtained which dries and is fixed on the phthalocyanine coated paper by absorption.

Although specific components have been described in the above examples, other binders, phthalocyanines, and proportions of materials may be used with similar results. Further, other additives which sensitize, synergize, or in other ways affect the pate of this invention may be added. For example, an antiblocking agent such as silica pigment may be employed to eliminate adhesion between rolled paper layers.

Various other modifications will become apparent to those skilled in the art upon reading of this disclosure. These are intended to be encompassed within the scope of this invention.

What is claimed is:

1. An electrophotographic material which comprises a phthalocyanine pigment said pigment being selected from at least one member of the group consisting of alpha phthalocyanine, beta phthalocyanine, and X-form phthalocyanine; and a binder for said pigment comprising from about 6 to about 13 parts, by weight, of an alkyd-acrylate resin blend, from about 2 to about 4 parts, by weight, of a silicone resin, and from about 6 to about 13 parts, by weight, of a film forming chlorinated hydrocarbon.

2. The material as defined in claim 1 wherein said phthalocyanine pigment is metal-free.

3. The material as defined in claim 1 further comprising an antiblocking agent.

4. The material as defined in claim 3 wherein said antiblocking agent comprises a silica pigment.

5. The material as defined in claim 1 which comprises about 1 to 2 parts, by weight, of a phthalocyanine pigment said pigment being selected from at least one member of the group consisting of alpha phthalocyanine, beta phthalocyanine, and X-form phthalocyanine; about 2-4 parts by weight of silicone resin; about 6-13 parts, by weight, of chlorinated hydrocarbon; and about 4 12 parts, by weight, of the resin blend.

6. The material as defined in claim 1 which comprises about 1 part, by weight, of said phthalocyanine pigment; about 2.5 parts, by wei ht of said silicone resin; about 7 arts, by weight, of sai chlorinated hydrocarbon; and about 7 parts, by

weight, of said resin blend.

7. An electrophotographic plate which comprises a photoconductive layer positioned on a substrate material, said photoconductive layer comprising a phthalocyanine pigment said pigment being selected from at least one member of the group consisting of alpha phthalocyanine, beta phthalocyanine, and X-form phthalocyanine; and a binder for said pigment comprising from about 6 to about 13 parts, by weight, of an alkyd-acrylate resin blend, from about 2 to about 4 parts, by weight, of a silicone resin, and from about 6 to about 13 parts, by weight, of a film-forming chlorinated hydrocarbon.

8. The plate as defined in claim 7 wherein said substrate material comprises paper.

9. The plate as defined in claim 7 wherein said substrate material comprises a film base.

10. The plate as defined in claim 7 wherein said substrate material comprises conductive treated paper.

11. The plate as defined in claim 7 wherein said substrate material comprises a plastic material.

12. The plate as defined in claim 7 wherein said photoconductive layer is overcoated.

13. A self-supporting photoconductive layer which comprises a phthalocyanine pigment said pigment being selected from at least one member of the group consisting of alpha phthalocyanine, beta phthalocyanine, and X-form phthalocyanine; and a binder for said pigment comprising from about 6 to about 13 parts, by weight, of an alkyd-acrylate resin blend, from about 2 to about 4 parts, by weight, of a silicone resin, and from about 6 to about 13 parts, by weight, of a filmforming chlorinated hydrocarbon.

14. A process for forming a latent image which comprises charging a photoconductive layer which comprises a phthalocyanine pigment selected from at least one member of the group consisting of alpha-phthalocyanine, beta-phthalocyanine, X-form phthalocyanine; and a binder for said pigment comprising from about 6 to about 13 parts, by weight, of an alkyd-acrylate resin blend, from about 2 to about 4 parts, by weight, of a silicone resin and from about 6 to about 13 parts, by weight, of a film forming chlorinated hydrocarbon, and exposing said layer in imagewise configuration.

15. The process as defined in claim 14 wherein said photoconductive layer is overcoated with an insulating composition.

16. A process for forming a latent electrostatic charge pattern which comprises electrostatically charging the electrophotographic material of claim 1 and exposing said material to a pattern of activating electromagnetic radiation.

17. A process for forming a latent electrostatic charge pattern on the electrophotographic plate as defined in claim 5 which comprises electrostatically charging the photoconductive layer of said plate and exposing said layer to a pattern of activating electromagnetic radiation.

18. An electrophotographic process which comprises electrically charging the electrophotographic plate as defined in claim 5, exposing said plate to an image pattern to be reproduced, and developing said image.

19. An electrophotographic process which comprises passing the electrophotographic plate as defined in claim 7 at least twice through a cycle comprising charging and exposing said plate to a pattern of activating electromagnetic radiation and developing with electrostatically attractable colored material.

a w a a a: 

2. The material as defined in claim 1 wherein said phthalocyanine pigment is metal-free.
 3. The material as defined in claim 1 further comprising an antiblocking agent.
 4. The material as defined in claim 3 wherein said antiblocking agent comprises a silica pigment.
 5. The material as defined in claim 1 which comprises about 1 to 2 parts, by weight, of a phthalocyanine pigment said pigment being selected from at least one member of the group consisting of alpha phthalocyanine, beta phthalocyanine, and X-form phthalocyanine; about 2-4 parts by weight of silicone resin; about 6-13 parts, by weight, of chlorinated hydrocarbon; and about 4-12 parts, by weight, of the resin blend.
 6. The material as defined in claim 1 which comprises about 1 part, by weight, of said phthalocyanine pigment; about 2.5 parts, by weight, of said silicone resin; about 7 parts, by weight, of said chlorinated hydrocarbon; and about 7 parts, by weight, of said resin blend.
 7. An electrophotographic plate which comprises a photoconductive layer positioned on a substrate material, said photoconductive layer comprising a phthalocyanine pigment said pigment being selected from at least one member of the group consisting of alpha phthalocyanine, beta phthalocyanine, and X-form phthalocyanine; and a binder for said pigment comprising from about 6 to about 13 parts, by weight, of an alkyd-acrylate resin blend, from about 2 to about 4 parts, by weight, of a silicone resin, and from about 6 to about 13 parts, by weight, of a film-forming chlorinated hydrocarbon.
 8. The plate as defined in claim 7 wherein said substrate material comprises paper.
 9. The plate as defined in claim 7 wherein said substrate material comprises a film base.
 10. The plate as defined in claim 7 wherein said substrate material comprises conductive treated paper.
 11. The plate as defined in claim 7 wherein said substrate material comprises a plastic material.
 12. The plate as defined in claim 7 wherein said photoconductive layer is overcoated.
 13. A self-supporting photoconductive layer which comprises a phthalocyanine pigment said pigment being selected from at least one member of the group consisting of alpha phthalocyanine, beta phthalocyanine, and X-form phthalocyanine; and a binder for said pigment comprising from about 6 to about 13 parts, by weight, of an alkyd-acrylate resin blend, from about 2 to about 4 parts, by weight, of a silicone resin, and from about 6 to about 13 parts, by weight, of a film-forming chlorinated hydrocarbon.
 14. A process for forming a latent image which comprises charging a photoconductive layer which comprises a phthalocyanine pigment selected from at least one member of the group consisting of alpha-phthalocyanine, beta-phthalocyanine, X-form phthalocyanine; and a binder for said pigment comprising from about 6 to about 13 parts, by weight, of an alkyd-acrylate resin blend, from about 2 to about 4 parts, by weight, of a silicone resin and from about 6 to about 13 parts, by weight, of a film forming chlorinated hydrocarbon, and exposing said layer in imagewise configuration.
 15. The process as defined in claim 14 wherein said photoconductive layer is overcoated with an insulating composition.
 16. A process for forming a latent electrostatic charge pattern which comprises electrostatically charging the electrophotographic material of claim 1 and exposing said material to a pattern of activating electromagnetic radiation.
 17. A process for forming a latent electrostatic charge pattern on the electrophotographic plate as defined in claim 5 which comprises electrostatically charging the photoconductive layer of said plate and exposing said layer to a pattern of activating electromagnetic radiation.
 18. An electrophotographic process which comprises electrically charging the eleCtrophotographic plate as defined in claim 5, exposing said plate to an image pattern to be reproduced, and developing said image.
 19. An electrophotographic process which comprises passing the electrophotographic plate as defined in claim 7 at least twice through a cycle comprising charging and exposing said plate to a pattern of activating electromagnetic radiation and developing with electrostatically attractable colored material. 